Color photography



y 1938- c. c. SMiTH ET AL O 2,115,886

COLOR PHOTOGRAPHY Filed Jan. 8, 1936 BLOOD CORPUCLE1- l= z" g. 2.

A? magmmwvs ,EEAL 3 CORPQjCLE LAYER Z FILM r CA 1 LIGHT IN VEN TORS CHALMERS C. SMITH. R P/NHER AY H ATTORNEYS.

Patented May 3, 1938 coma rno'rooaarnr Chalmers 0. Smith, Glendale, and Ray H. Pinker,

Los Angeles, Calif. I

Application January 8,

6 Claims.

Our invention relates to color photography,

and more particularly to photographs, both positive and negative, utilizing for the production of color an "irregular color screen.

Amongthe objects of our invention are: To provide a mosaic wherein the elementary area is exceptionally small; to provide a color screen of high transparency; to provide a color screen of minimum thickness; to provide a color screen wherein the elements are substantially of equal size; to provide a color screen wherein the elemental elements are, on the average, closely adjacent, thus requiring no filler; to provide a color screen which is available for quantity production and which is especially adapted for use with motion picture film; to provide a means and method for photographing motion pictures in color with a greater detail than heretofore obtained; to provide an improved, positive and negative film stock for the production of positive and negative photographis in color; to provide a means and method for printing colored photographs,- especially useful in motion picture production; and to provide an improved system of 25 color photography which is cheap and which requires substantially no different treatment than that of ordinary blackand white practice.

' Our invention possesses numerous other objects-and features of advantage, some of which, together with the foregoing, will be set forth in the following description of specific apparatus embodying and utilizing our novel method. It is therefore to be understood that our method is applicable to other apparatus, and that we do not limit ourselves, in any way,to the apparatus of the present application, as we may adopt various other apparatus embodiments, utilizing the method, within the scope of the appended claims.

In the drawing,

Figure 1 is a diagrammatic perspective view of the mosaic of our, invention as applied to film stock. Figure 2 is a diagram showing the relationship of the various layers.-

The use of screens for the production of colored photographs, especially transparencies, is old, two kinds of screen being known in the art; first, a regular screen, one whichis ruled or impressed with a regular series of discs, lines or squares, each one of the series being of a different color; second, an irregular screen, one in which a series of colored particles are strewn haphazard over the foundation stock. All of the screens, however, have one feature in common; they are directed toward the end of creating a 86 color pattern composed, for example, of the three 1936, Serial No. 58,108 (Cl. 95-21 primary colors, red, green and blue-violet, which transmit their respective colored lights.

Our invention has to do solely withthe'second class of screens, namely, the irregular type. Perhaps the best example of the prior art irregular screens is that used on the Autochrome plates. The autochromeplate isprovided with a screen comprising a single layer of starch grains deposited upon a stock or foundation material preferably transparent and is usually overlaid 10 with a panchromatic emulsion. The grains are usually of potato starch varying in size between .01 and .02 millimeter, and after the grains have been dyed and deposited, they are. usually fiattened by means of rollers, to fill up the inter- 15 stices, and then varnished to hold them inposition. In some cases such rolling does not completely fill up the interstices, and a filler, such as lamp black, is added in order to block out areas uncovered by the starch grains. The grains are 20 first divided into groups, each group dyed a different color, and then thoroughly mixed before deposition to give a haphazard color pattern. The colors used usually are red, green, and blueviolet. 25

There are a number of disadvantages to the starch grain screen, particularly when used for motion picture work. i The starch grains are relatively large, .so that with the tremendous magnification necessary in motion picture projection, the grains either are actually seen by those close to the screen or they are so large as to render a sharp outlines distinctly fuzzy to those seated far enough away from the screen so that they cannot actually see the grains. It is therefore obvious that for motion picture work screen-elemerits much smaller than the starch grains are necessary Furthermore, starch grains are, first, irregular in shape; and second, vary greatly in size, the 40 larger grainsbeing somewhat more than three times the diameter of the smaller. This difference in size and shape mitigates against correctness in color because it is possible, andquite common, to have, forexample, an extremely large grain of one color adjacent an extremely small grain of one of the other colors. Such an arrangement, besides givingan untrue colorvalue at that point,- also prevents sharp detail, especially under high magnification. It is therefore, especially for motion picture work, extremely desirable that all the elements of a successfulmo tion picture screen be of uniform size and,.preferably, of a regular shape; in'other words, each 5 element should be substantially identical with every other element except-for color.

One other featuremust be taken into account, that is, the density of the elements. Starch grains have a relatively low light transmission, and as a consequence the amount of light used for exposure must be high, inasmuch'as this light must first pass through the screen before reaching the light-sensitive emulsion; The exposure for the starch grain type of negative must be approximately ten times greater than the exposure necessary for the same emulsion alone.

We haveinvented a photographic medium having associated therewith a screen wherein the elements are substantially all the same shape, the same size, and in which the size of the elements is only from .0075 millimeter to .003 millimeter varying in accordance with the class of material used. The elements of any one species of material vary little in size or shape. Furthermore, the screen of our invention comprises elemental material having a relativey high light transmission value.

In broad terms, our invention comprises a color screen composed of a mosaic of blood corpuscles,

preferably from mammals, deposited on a'founda- I tion material in such a manner that their thinnest aspect is presented to the light path, and

with their peripheries substantially in contact. We prefer to dye the corpuscles with various colors before deposition, and any number of colors may be used although we prefer to simplify the process and use the three primary colors, red, green and blue-violet. It is: well known that blood corpuscles are disc shaped and thin in one dimension.

Long diameters of red blood cells are as follows:

We also prefer to protect the screen with a transparent layer, and in this respect we may incorporate in the protecting material a preservative,'such as formaldehyde. The screen is'then covered with a thin panchromatic emulsion, and in many instances we may prefer to add over the panchromatic emulsion a thin layer of orthochromatic emulsion. Y

For motion picture work we prefer toutilize both positive and negative film stock and make a negative showing complementary colors, and then print optically to obtain a positive which may then be used for motion picture projection in a standard machine. Inasmuch as our screen has a relatively high light transmission value, no change is necessary in camera or projector, and in fact the negative filmrequires only an exposure'double that of the emulsion alone; or, to eifect the same 'result, thesame time maybe used with only one stop wider opening on the camera lens. Our system is therefore ideally adapted for motion picture production, and we will describe in greater detail the production of motion picture color films in accordance with our invention.

We prefer to obtain blood corpuscles from sheep, inasmuch as large quantities of sheep blood are available from slaughter houses. The, corpuscles may be accumulated by centrifuging, and if desired may be decolorlzed, although this is not always necessary. They may be handled in an isotonic salt solution, or their natural serum, and are perfectly stable in solutions of .8 per cent to 2.0 per cent of sodium chloride, or similar salts. The largest diameter of sheep corpuscles is approximately .003 millimeter, although this may be varied slightly by the treatment in the stabilizing element due to osmotic changes, and they may be either slightly swollen or slightly shrunken, as it may appear to be desirable. In this stage'they may either be dyed directly or they may first be impregnated with a mordant solution, such as potassiumiodlde. The corpuscles may then be separated into groups and dyed.

Various dyes well known in the art may be used to give the proper color to the blood cells. As an example, many of the dyes heretofore useful in dyeing biological specimens are suitable, such as methyl red, methyl green,,the "Pinatype group, which includes natural carmine, lanafuchsin, BB and SL, indolinblue, acid yellow or quinoline yellow, and those dyes belonging to the haematoxylin or logwood group. It will'be obvious to those skilled in the art to select dyes of colors cooperating to give them the desired color .pattern. We prefer, for motion picture work, to use three colors, red, green, and blue violet, irrespective of the particular dyes'used.

The dyed corpuscles are then mixed and they may, if desired, be deposited on the film stock I, usually a cellulose derivative, directly from liquid solution by dipping. In the case of film, continuous progression through a bath containing a heavy suspension of corpuscles is a satisfactory method of coating. The corpuscles, because of their disc shape, have a tendency to cling to the surface of the stock in a single layer 2, and also tend to gravitate together so that when the film stock is drained, a single thin layer is deposited thereon with practically no openings between the corpuscles, the corpuscles touching each other, with their thinnest aspect presented to the plane of the stock.

The variously colored corpuscles may or may not be .depositedin equal amounts; in fact, the type of mixture will be determined, to some extent, on the use of which the stock'is to be put; and we contemplate the use of various mixtures, one of which, for example, known to'be a good mixture for prior screens, is a mixture in the ratio of four green elements, three red elements and two blue elements. The mixture will naturally vary in accordance with the type of lights contemplated jfor taking the photographs and with the type of field to be photographed.

In any event, after the stock is dried the screen thereon is protected by an overlay of a thin layer 3 of alcohol and albumen, or formaldehyde and albumen, thus covering the corpuscle layerwith taining a preservative in order to prevent disintegration of the corpuscles. The preferred emulsion coating is a panchromatic emulsion 4 directly over the seal, over-coated with an orthochromatic emulsion in order to widen the color range.

The film is then exposed from the back in an ordinary camera so that the light passes through the screen before reaching the emulsion. Due to the fact that blood corpuscles have an extremely high light transmission value, an exposure of only double that of the emulsion alone is needed; and with motion picture cameras, with relatively fixed timing, all that is necessary is the use of one a thin impervious seal, this seal, however, conextra stop opening on the iris diaphragm, or similar device.

The exposed film is then developed in ordinary negative solutions and produces, of course, a color negative; that is, the film is negative as far as the emulsion is concerned, and complementary in color range to the original.

It is of course obvious that the response will vary in accordance with the illumination of the picture field, daylight pictures differing from indoor, artiflcially illuminated, pictures. Prints may then be made directly from the negative with an optical printer, and we prefer to utilize a slight movement in the optical system so that an overlap is obtained between elements of the positive and negative screens.

There are various ways of obtaining this overlap, either by movement of the printer light or the optical lens system itself, with relation to the film being printed. In the printer, a light source may be used having substantially the characteristics of the light by which the negative was-exposed, daylight being approximated by various illuminant combinations and filters. Such combinations may be built up, as is known in the art, to give a light which approximates within 2 per cent the spectrum of daylight.

A negative film produced under our invention will have a light transmission value of approximately 34 per cent, and the positive a transmission of approximately 40 per cent. These values are not far from the transmission values of ordinary black and white films, and as a consequence, in the projection of these prints, no excess light is necessary, this of course being mainly due to the fact that the corpuscles are of extremely thin section.

The sizes of the corpuscles may be regulated, to some extent, by the particular animal from which the corpuscles were taken, those drom all mammals, except the camel, being preferred, as the camel has oval corpuscles. We do not, however, wish to be excluded from the use of oval corpuscles as there may be screen uses in which an oval corpuscle would be desirable, and while we intend to utilize, for quantity production, corpuscles easily obtained in large quantities, 'for certain experimental uses, at least, other corpuscles may be' desirable. important as small size.

Shape is not nearly as Furthermore, we have found that the desired color ratios may be obtained by a l-l--l corpuscleratio provided corpuscles from different animals are used, utilizing corpuscles having different average sizes thus'obtaining the color ratio desired by the difference in area occupied by the different corpuscles. This is highly practical because we have a wide size range fromwhich to choose, even though all of them are within the average grain size of the emulsions used.

The use of a l-1-l corpuscle ratio allows us to avoid clumping, as it is called, where from 2-14 particles of one color cluster around a single unit of another color. Even with no precautions against it, clumping with our screen material is not so important as in screens having larger particle sizes as the size of the clump as a whole in our screen is relatively small.

We claim:

1. Means for recording colored objects comprising a mosaic screen of mixed blood corpuscles dyed' in differing colors, and a light sensitive material positioned to receive light passing 3. A color screen in the form of a mosaic layer,

of blood corpuscles comprising at least two corpuscle groups dyed a different color and having a different average size.

4. A color screen in the form of a mosaic layer of blood corpuscles comprising at least two corpuscle groups dyed a different color and from a different animal.

5. A color screen in the form of a'mosaic layer of blood corpuscles comprising at least two corpuscle groups dyed a different color and having difierent physical characteristics.

6. The method of distributing color in a mosaic screen of blood corpuscles which comprises dyeing corpuscle groups having a difierent average slze in different colors, and depositing them in a single layer in a 1--1 ratio.

CHALMERS 0. SMITH. RAY H. PINKER. 

